Featured Research

from universities, journals, and other organizations

Rare Volcanic Plumes Create Uncommonly Dangerous Ash Flows

Date:

March 14, 2006

Source:

University of Illinois at Urbana-Champaign

Summary:

Three unique photographs of a recent volcanic eruption in a remote part of Ecuador show a plume unlike any previously documented, and hint at a newly recognized hazard, say scientists at the University of Illinois at Urbana-Champaign.

Share This

Three unique photographs of a recent volcanic eruption in a remote part of Ecuador show a plume unlike any previously documented, and hint at a newly recognized hazard, say scientists at the University of Illinois at Urbana-Champaign.

Related Articles

“The usual volcanic plume consists of a stalk capped with an umbrella, and resembles the mushroom of an atom bomb blast,” said geology professor Susan Kieffer, “but the umbrella on this plume was wavy, like the shell of a scallop.”

In a paper scheduled to appear March 15 in the journal Geophysical Research Letters, Kieffer, theoretical and applied mechanics professor Gustavo Gioia, and graduate student Pinaki Chakraborty explain what might have caused the umbrella to scallop, a task made more difficult by the scarcity of information.

“We had never seen a scalloped umbrella before,” said Kieffer, who holds a Charles R. Walgreen Jr. Chair at Illinois. “Unusual conditions must have existed in the volcanic plume that formed this umbrella.”

Located about 100 kilometers from Quito, Ecuador, Volcán Reventador – Spanish for “one that explodes” – lived up to its name on the morning of Nov. 3, 2002. Following seven hours of seismic activity and billowing steam, the summit cone exploded and sent a stream of ash, called a pyroclastic flow, several kilometers down nearby valleys. While traveling close to the ground, the ash heated the surrounding air, which became buoyant as in a hot-air balloon. The air rose in a volcanic plume, carrying the ash with it.

“A volcanic plume rises until the atmosphere becomes so thin that the mixture of air and ash loses buoyancy and starts to spread laterally, forming an umbrella,” Gioia said. “The umbrella spreads and cools for a long time before the ash begins to fall gradually.”

But instead of the usual hot ash, the Reventador eruption appears to have been laden with steam and a fairly cool ash from the destruction of the summit cone. The unusually cool umbrella could not spread for a long time. It rapidly became a heavy mixture of air, steam and ash hovering precariously over the lighter air below.

“When a heavier fluid is placed on top of a lighter one, you might say that the fluids want to be reversed,” said Chakraborty, the paper’s lead author. “The ensuing tug of war between gravity and the viscosity of the fluids results in a wavy instability that pulls the heavier fluid on a fast sinking course.”

In laboratory experiments, the fluids are initially at rest, and the wavelength of the instability is a fraction of an inch. But the mixture of air, steam and ash in the Reventador umbrella was turbulent, with many fast, locally swirling motions.

“Turbulence magnifies the wavelength,” Chakraborty said. “It gave the Reventador umbrella its distinctive scallops, which were hundreds of meters in wavelength.”

“Our analysis suggests that the Reventador umbrella collapsed rapidly, forming new and especially dangerous ash flows,” said Kieffer, who is also a professor in the university’s Center for Advanced Study, one of the highest forms of campus recognition.

Originating far from the summit cone, these new ash flows must have helped spread the damage caused by the eruption. They must have been uncommonly energetic, because the ash fell from the umbrella, which was 10 kilometers high.

“For all we know, these flows were responsible for broken petroleum pipelines,” Chakraborty said. “The flows might also have contributed to the early phases of a shutdown of Quito airport that lasted more than a week.”

More From ScienceDaily

More Earth & Climate News

Featured Research

Mar. 3, 2015 — Attendance at schools exposed to high levels of traffic-related air pollution is linked to slower cognitive development among 7- to 10-year-old children in Barcelona, according to a new ... full story

Mar. 3, 2015 — While studying a ground-nesting bird population near El Reno, Okla., a research team found that stress during a severe weather outbreak of May 31, 2013, had manifested itself into malformations in ... full story

Mar. 3, 2015 — Researchers studied quartz from the San Andreas Fault at the microscopic scale, the scale at which earthquake-triggering stresses originate. The results could one day lead to a better understanding ... full story

Mar. 3, 2015 — The 3-D printing scene, a growing favorite of do-it-yourselfers, has spread to the study of plasma physics. With a series of experiments, researchers have found that 3-D printers can be an important ... full story

Mar. 3, 2015 — Researchers have developed a new way of rapidly screening yeasts that could help produce more sustainable biofuels. The new technique could also be a boon in the search for new ways of deriving ... full story

Mar. 3, 2015 — For almost a century, scientists have been puzzled by a process that is crucial to much of the life in Earth's oceans: Why does calcium carbonate, the tough material of seashells and corals, ... full story

Mar. 3, 2015 — Major cities in the UK are falling behind their international counterparts in terms of their use of smart technologies, according to a new study. The research has found that smart cities in the UK, ... full story

Mar. 3, 2015 — To simulate chimp behavior, scientists created a computer model based on equations normally used to describe the movement of atoms and molecules in a confined space. An interdisciplinary research ... full story

Mar. 3, 2015 — Rather than just waiting patiently for any pollinator that comes their way to start the next generation of seeds, some plants appear to recognize the best suitors and 'turn on' to increase the chance ... full story

Featured Videos

Looted and Leaking, South Sudan's Oil Wells Pose Health Risk

AFP (Mar. 3, 2015) — Thick black puddles and a looted, leaking ruin are all that remain of the Thar Jath oil treatment facility, once a crucial part of South Sudan&apos;s mainstay industry. Duration: 01:13
Video provided by AFP

Related Stories

Feb. 3, 2015 — Volcanic ash poses a significant hazard for areas close to volcanoes and for aviation. For example, the 2010 eruption of Eyjafjallajökull, Iceland, clearly demonstrated that even small-to-moderate ... full story

Apr. 2, 2013 — Studying volcanos can be hazardous work, both for researchers and aircraft. To penetrate such dangerous airspace, unmanned aerial vehicles (UAVs), especially those with electric engines that ingest ... full story

Nov. 21, 2012 — Less than two percent of the earth's fossils are preserved in volcanic rock, but researchers have identified a new one: the skull of a rhino that perished in a volcanic eruption 9.2 million ... full story

Dec. 9, 2010 — The eruption of the Icelandic volcano Eyjafjallajökull in April this year resulted in a giant ash cloud, which -- at one point covering most of Europe -- brought international aviation to a ... full story

Apr. 22, 2010 — More accurate data about the potential danger to aircraft from volcanic plumes is being gathered by scientists. As another plume is due to sweep across the UK in the next few days, researchers are ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.